Method of recovering desirable liquefiable hydrocarbons



Jan. 8, 1952 H. M. NELLY, JR

METHOD OF RECOVERING DESIRABLE LIQUEFIABLE HYDROCARBONS Filed May 15, 1947 Ju/ye drum Pump

Fracfiormfa- Separafor l rjecflon Well Producing Remover /3 Pressure Separafar 3nnentor Harry M. may J/: W 1 WM.

attorney:

Patented jan. 8, 1952 METHOD OF RECOVEBING DESIRABLE LIQUEFIABLE HYDROCARBON S Henry Meredith Nelly, J r., Houston, Tex, assignor' to J. F. Pritchard & 00., Kansas City, Mo., a

corporation of Missouri I Application May 15, 1947, semi No.- 748,358

3 Claims. (01. 1cc21) This invention relates to a method of recovering desirable liquefiable hydrocarbons from a fiow' of high pressure natural gas such as the flow from a highpressure well and particularly where the residue gas is to be used for pressuring producing formations.

It is well known that high pressure natural gas contains profitable quantities of desirable liquefiable hydrocarbons but such hydrocarbons, for practical purposes, must be recovered at substantially lower pressure than the pressure of the formation in which the residue gas is to be used. Consequently, the pressure of the residue gas must be raised to a pressure above the pressure of the formation in which it is to be used.

Heretofore this has required expensive compressor equipment and much horsepower to raise the pressure of the residue gas to the required injection pressure. Consequently, recovery of such hydrocarbons may not be profitable where it is necessary and desirable to use the residue gas for pressurin high pressure formations.

Therefore, the principal objects of the present invention are to provide a method for recovering desirable liquefiable hydrocarbons from high pressure natural gas, and to provide an inexpensive method for injecting the residue gas into a producing formation at the required pressure In accomplishing these and other objects of the invention hereinafter pointed out, I have provided improved structure and method of operation illustrated in the accompanying drawing wherein:

The single figure is a diagrammatic view of my improved apparatus for removing desirable liquefiable hydrocarbons and raising the pressure of the residue gas to the desired injection pressure.

Referring more in detail to the drawings:

I designates a well drilled into a natural gas producing formation and wherethrough the formation liquid is discharged in a gaseous fiow containing desirable liquefiable hydrocarbon fractions, the flow being discharged from the well through a tubing 2 to which is connected a fiow pipe 3 leading from the well to the gas processing apparatus embodying the features of the present invention. 4 designates a repressuring well having an intalge pipe 5 through which residue gas is returned to a producin formation which may be the formation into which the producing well is drilled or another formation which is to be repressured with the residue gas produced from the well I.

Gaseous hydrocarbons from the well I are directed through the pipe 3- at substantially full well head pressure and temperature which, by way of an example, may be 3100 p. s. i. g. and 180 F. to a precooler 6 wherein the flow of gas 2 is reduced to as low a temperature as possible without the formation of hydrates. By way of illustration, the temp-erature'may be reduced by the use of water to F. and the gas is delivered into a high pressure separator 7 which is connected with the precooler 6 by a pipe 8. Upon being dischargedto the high pressure separator, any liquids contained in the gas flow or resulting incidental to reduction in temperature, mainly heavy distillate material, settle to the bottom of the separator and are discharged through a pipe 9 leading to a fractionating apparatus which is indicated at Ill. The gas constituent raises to the top of the separator and is discharged through a pipe II to a carbon dioxide and hydrogen sulfide removal unit l2, after which the-vapor is discharged through a pipe I3 to a dehydrator unit l4 wherein thedew point of the vapor is reduced, the vapor being discharged through a pipe 15.

If hydrogen sulfide and carbon dioxide are not present in the gas or if the composition of the vapor is such that its boiling point is higher than the solidification point of carbon dioxide and hydrogen sulfide, the hydrogen sulfide and carbon dioxide removal unit I2 may be omitted and the vapors passed directly to the dehydrator.

The flow of vapors in the pipe Isis diverted for flow through pipes l6 and ll leading to heat exchangers l8 and I9 wherein the heat exchange mediums are the residue gas and the recovered liquefied hydrocarbons respectively, the purpose being to recover the refrigeration of the fluids before they are discharged for injection purposes and to the fractionating apparatus H]. The cooled vapor passing from the heat exchanger I8 is discharged at a low temperature of, for example, 15 F. through a pipe 20 to a refrigerating unit 2| where the temperature of the vapor is reduced by contact with a refrigerating medium such as ethane admitted through the refrigeration unit through a pipe 22 and discharged through a pipe 23, which pipes are connected with suitable refrigerating machinery (not shown). The vapor is discharged from the refrigerating unit through a pipe 24 at a temperature, for example, -10 F. The flow through the heat exchanger I9 is discharged through a pipe 25 at, for example, a 20 temperature, the pipe 25 being connected with the pipe 24 so that the respective flows are reunited and discharged through a pipe 26 into aseparator 21.

Since the vapor has been cooled to the point for the recovery of the natural gasoline, butane and propane constituents, such constituents gravitate as liquids tothe bottom of the separator 21 and are discharged through a pipe 28 for flow through the heat exchanger l9 and discharged through a pipe 29 that is connected with the pipe 9 so that the desirable liquefied hydrocarbons resulting in'the separator 2? are conducted along with those from the separator 7 to the fractionating apparatus ill for the production of the desired materials such as distillate, natural gasoline, butane and propane. The vapor from the separator 21 is discharged through a pipe 33 that is connected with a heat exchanger 3i wherein the vapor is reduced to a lower temperature, for example, 45 F. through extraction of the refrigeration from the repressure fluid. The vapor being discharged from the heat exchanger through a pipe 32 is throttled through a valve 33 to a pressure at which complete condensation of the vapor may be effected with a minimum extraction of latent heat. For example, the vapors may be expanded to a pressure slightly below the critical pressure of the mixture, thus setting the temperature of condensation slightly below the critical temperature where the latent heat is zero, the proximity of the operating temperature to the critical temperature depending upon the ability to control the condensing temperature and pressure,

The vapor upon being throttled through the valve 33 is further cooled due to the Joule-Thomson effect. The expanded vapor at a temperature of -35 F. and at a pressure of 680 p. s. i. g. is discharged through a refrigerating unit 34 where the temperature is reduced to a temperature of 95 F. by contact with ethane, which ethane is delivered from a suitable refrigeration apparatus (not shown) through a pipe 35 and returned through a pipe 36. In the refrigerating unit the temperature is brought to a 95 F.

temperature and the flow is discharged at a pressure of substantially 670p. s. i. g. through a pipe 31 that is connected with a surge drum 38.

The major portion of the vapor is liquefied as a 4 result of the reduced temperature and lower pressure. The liquid gravitates to the bottom of the surge drum and is discharged through a pipe 39 to the inlet of a pump M] which raises the pressure of the liquid to that necessary for return of the liquefied vapor to the formation to be repressured. Any vapor remaining is vented from the top of the surge drum through a pipe 4 I.

The liquid under the pressure necessary for return to the formation, is discharged from the pump through a pipe 42 which leads through the heat exchanger [8. A part of the flow is diverted for flow through the heat exchanger 3 I through a pipe 43 and flow from the heat exchanger is conducted through-a pipe 44 back to the pipe 42, the flow being diverted by a valve 45 that is inserted in the pipe 42 between the connections of the pipes 43 and 44 therewith,

By lique'fying the residue gas and raising the pressure of the liquefied gas to the pressure necessary for repressure injection; for example, in the illustrated instance to 3800 p. s. i. g., I am enabled to treat a high pressured gas flow to recover the desirable liquefiable constituents and economically return the residue gas for injection purposes since expensive compressors and power necessary to raise the liquid gas to the required pressure are not required.'

With the present invention the pressure is readily re-established by a simple pump apparatus while the residue gas is in liquid form and capable of being raised to the desired pressure with a minimum of power.

It is to be understood that the pressures and temperatures are given for examples and that the temperatures and pressure may be varied to meet the conditions under which the apparatus may be operated to obtain the desired results.

What I claim and desire to secure by Letters Patent is:

1. The method of obtaining desirable liquefiable petroleum hydrocarbons from a producing formation including flowing the gas under pressure from the formation to the surface of the ground, precooling the gas at substantially the pressure of the flow from said formation to effect stripping of the gas of the desirable liquefiable hydrocarbons, expanding the stripped gas to a substantially lower pressure, refrigerating the stripped gas to effect substantial condensation at the expanded pressure, pumping the liquefied stripped gas to the formation at a pressure higher than the pressure of said petroleum hydrocarbons in the formation, and passing the liquefied stripped gas in heat exchange relation with the gas fiow prior to extraction of the desirable liquefiable hydrocarbons for the precooling of the gas fiow.

2. The method of obtaining desirable liquefiable hydrocarbons from a producing formation including flowing the gas under pressure from the formation to the surface of the ground, p'recooling the gas at substantially the pressure of the fiow from said formation to effect stripping of the gas of the desirable ,liquefiable hydrocarbons, expanding the stripped gas to a substantially lower pressure, refrigerating the expanded gas to effect substantial liquefaction of said gas at the expanded pressure, pumping the liquefied stripped gas to the formation at a pressure above the pressure of the formation for returning the liquefied stripped gas to the formation, and passing the stripped liquefied gas in heat exchange relation with a part of gas flow prior to extraction of the desirable liquefiable hydrocarbons for said precooling of the gas flow, and passin the desirable liquefied hydrocarbons into heat exchange relation with the remainder of the gas flow.

3. The method of obtaining desirable liquefiable petroleum hydrocarbons from a producing formation including flowing the gas under pressure from the formation, cooling the gas at substantially the pressure of the flow from said formation to strip the gas by condensation of the desirable liquefiable hydrocarbons, removing the condensate from the stripped gas, expanding the stripped gasto a substantially lower pressure, refrigerating the stripped gas to effect liquefaction of the stripped gas and pumping the stripped liquefiedgas to the formation at a pressure higher than the pressure of said petroleum hydrocarbons in the formation.

HENRY MEREDITH NELLY, JR.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,258,015 Keith et a1. Oct. 7, 1941 2,297,832 Hudson Oct. 6, I942 2,361,012 Cole et a1. Oct. 24, 1944 2,374,104 Kirkbride Apr. 17, 1945 

3. THE METHOD OF OBTAINING DESIRABLE LIQUEFIABLE PETROLEUM HYDROCARBON FROM A PRODUCING FORMATION INCLUDING FLOWING THE GAS UNDER PRESSURE FROM THE FORMATION, COOLING THE GASE AT SUBSTANTIALLY THE PRESSURE OF THE FLOW FROM SAID FORMATION TO STRIP THE GAS BY CONDENSATION OF THE DESIRABLE LIQUEFLABLE HYDROCARBONS, REMOVING THE CONDENSATE FROM THE STRIPPED GAS, EXPANDING THE STRIPPED GAS TO A SUBSTANTIALLY LOWER PRESSURE, REFRIGERATING THE STRIPPED GAS TO EFFECT LIQUEFACTION OF THE STRIPPED GAS AND PUMPING THE STRIPPED LIQUEFIED GAS TO THE FORMATION AT A PRESSURE HIGHER 